Influence of drill mud on the microbial communities of sandstone rocks and well fluids at the Ketzin pilot site for CO₂ storage

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• 作者：Linda Pellizzari ; Tobias Lienen ; Monika Kasina…
• 关键词：Drill mud ; CO2 storage ; Reduced injectivity ; Sulfate ; reducing bacteria
• 刊名：Environmental Earth Sciences
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：76
• 期：2
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Geology; Hydrology/Water Resources; Geochemistry; Environmental Science and Engineering; Terrestrial Pollution; Biogeosciences;
• 出版者：Springer Berlin Heidelberg
• ISSN：1866-6299
• 卷排序：76

文摘

At a pilot site for CO₂ storage in Ketzin (Germany), a drastic decrease in injectivity occurred in a well intended for injection. This was attributed to an obstruction of the pore throats due to microbial degradation of the organic drill mud and subsequent iron sulfide (FeS) precipitation in the highly saline brine (240 g L−1). To better understand the biogeochemical processes, the response of the autochthonous microbial community to drill mud exposure was investigated. Pristine cores of two aquifers with different salinity were incubated under simulated in situ conditions (50 bar, 40 °C and 45 bar, 25 °C, respectively) and CO₂ atmosphere. For the first time, rock cores obtained from the CO₂ plume of the storage formation were investigated. The influence of acetate as a biodegradation product of drill mud polymers and the effectiveness of a biocide were additionally tested. Increased microbial diversities were observed in all long-term (8–20 weeks) incubations, even including biocide. Biofilm-like structures and small round-shaped minerals of probable microbiological origin were found. The results indicate that the microbial community remains viable after long-term CO₂ exposure. Microorganisms hydrolyzing cellulose polymers (e.g., Burkholderia spp., Variovorax spp.) biodegraded organic components of the drill mud and most likely produced low molecular weight acids. Although the effects of drill mud were less strong as observed in situ, it was demonstrated that acetate supports the growth of sulfate-reducing bacteria (i.e., Desulfotomaculum spp.). The microbial-induced precipitation of amorphous FeS reduced the injectivity in the near-well area. Therefore, when using organic drill mud, the well must be cleaned intensively to minimize the hazards of bacterial stimulation.